1. Field of the Invention
The invention relates to flat structural elements having a plurality of openings distributed according to a predetermined pattern and a packing composed of such structural elements.
2. Description of the Prior Art
From WO 90/10497 is known a vortex packing (multiple vortex mixing insert) which may be built up of layers of zigzag-folded metal sheets, the so-called pleated mats. The layers are parallel to an axis, the apparatus axis, while the folding edges are inclined to this axis. The layers are alternately so arranged that a system of channels is produced which often cross each other. The unfolded metal sheets have a chessboard-like pattern of substantially rhombic fields one half of which has the form of apertures. The other half forms structural elements of the packing. The open fields are somewhat smaller so that they have the form of island-like openings, and the closed fields are connected to each other at vertices by linear overlappings. The open fields form in the packing a second system of channels which often cross each other, the second system extending transversely to the first system. The folding edges extend--in the direction of the overlappings--along one part of the field margins.
In the known packing, the apertures in the metal sheets in the layers are made by stamping-out processes. It is mainly disadvantageous that nearly half of the starting material is lost and in addition, due to the expense involved with the stamping tools, there are limitations on the shape of the openings desirable as regards the method.